“Though I never anticipated this moment,” Smith said last month when Gov. Mark Dayton announced her appointment, “I am resolved to do everything I can to move Minnesota forward. … This is a difficult moment for us. But even now, I am filled with optimism for Minnesota.”

Democratic Sen. Doug Jones, who defeated Republican Roy Moore in an upset in deep red Alabama last month, was also sworn into office Wednesday by Vice President Mike Pence.

Four states — California, New Hampshire, Washington and, now, Minnesota — have women serving as both sitting senators. Smith is the 51st woman to ever serve in the Senate, according to the Rutgers University Center for American Women and Politics.

The Senate had two or fewer members who were women until 1993. The number of women in the chamber has increased tenfold since then, eventually hitting double digits in 2001.

There are 106 women serving in all of Congress, making up just less than 20% of all 535 seats in the House and Senate, according to the Rutgers University Center for American Women and Politics.

The 2017 global average of seats held by women in parliaments around the world was 24%, according to data from the World Bank.

The US stands at 102nd in female representation among the nations tracked by the World Bank — lower than countries like China, Iraq and Pakistan. Rwanda and Bolivia are the only countries with majority-female legislatures.